We specialize in the difficult trees that a bucket truck cannot get to which takes expert climbing skills. By the grace of God we have never had to make a claim on our insurance for either property damage or personal injury, though we do carry a 2 million dollar policy.
There are a number of reasons why people will remove a tree; it may have a bad lean toward the house or some other structure. If you do have a leaning tree and you want to hold off on removal for the time being, be sure and figure out a way to measure whether the tree is leaning more and more as time goes on. You may find that the lean will increase when the tree gets its heavy foliage in the summer or when the ground gets soaked in heavy rains.
If you do have a leaning tree, keep an eye on the ground at its base opposite the side of the lean. If it is showing a hump or cracks in the ground, then you have an immediate problem and the tree should be removed. The hump will show anytime but cracks usually only show in the dry weather during the summer. Leaning trees almost always fall directly toward the lean, even in very severe windy weather.
If a tree has carpenter ants (big black ants), in all probability there is rotting under the bark. Carpenter ants are a real bad sign, especially for an oak tree. Another problem is that the ants can move into the house and start chewing away at the wall studs and roof rafters. On a good note; we rarely see actual termites in trees.
Mushrooms growing out of a tree should be taken very seriously. Any fungal activity, especially at the base, spells trouble.If you can see a cavity at the trunk of the tree or on a limb itself you should consider removing that tree or that limb. The problem with a cavity is that the rot usually goes into the tree a lot further than it appears. We know this is true because we have cut through many a cavity after we have felled the tree only to find that the rot has moved most of the way to the center of the log. Beware of even small cavities. Loose bark is another telltale sign of an unhealthy situation. You may as well peel the bark back and take a look at what is under it; if you see new bark being formed you may be okay.
Another reason to remove an otherwise healthy tree is that it is growing too close to the house. If you live in snow and ice country you can have extensive breakage and damage to your roof.
A slow and ominous problem that could occur over time with a tree too close to your house is damage to your foundation. Foundation damage from a pine tree is rare because the roots tend to go downward but a lot of your oaks and other hardwoods can cause devastating foundation damage. If you live in a house built on independent piers like many of the wood frame houses in the South, roots should cause you no problems at all. If you own a brick house on a slab, watch for cracks in the bricks if there is a hardwood close by, especially if the roots are spreading out and showing on the surface of the ground.
Of course, if a tree is dead it should be removed as soon as possible. The longer you wait, the more dangerous and expensive the removal will be.